Microsoft Starts to Unify Win RT and Windows Phone

Taken from Paul thurrotts supersite for Windows article, here's what changed:

Cost. In keeping with a previous change to the Windows Phone Developer program, an individual developer account is now just $19 per year, while companies will pay $99 per year.
Existing developers get one more year for free. Developers who have already registered with both the Windows Store and Windows Phone developers programs will receive a code entitling them to another free year of the new unified developer program.
Windows Store developers are now Windows Phone developers. Registered Windows Store developers can now submit apps to the Windows Phone Store at no additional cost, using the same Microsoft account.
Windows Phone developers are now Windows Store developers. Registered Windows Phone developers can now submit apps to the Windows Store at no additional cost, using the same Microsoft account.
Developer dashboards. For now, the developer dashboards for Windows Store and Windows Phone developers will remain separate.
Students. No changes here: Students continue to be supported through the DreamSpark program.